Those chosen of God to follow Christ, are supposed to be fishers of men. What do fishers do?
To hunger and thirst after righteousness means to seek what is right in God’s eyes (as revealed in the Bible) and do what is right as it relates to the situations in our day-t0-day life. Christians are called to do what is right in God’s eyes.
Who do you show mercy upon? Upon someone who has wronged you and it is in your power to punish them (whether by words or deeds).
Christians are supposed to live peaceably with others and if they see brethren offended with each other, they are to help reconcile one with another. This is pleasing in the eyes of God to see His children taking care of each other.
Salt is used for adding flavour to food and for preservation of food. Salt regulates the water content in our bodies and lack of it can cause imbalances in normal functioning of our body. Believers are to act as a preservative in a world filled with sinful people whose every intent is evil (Psalm 14:3) and as a flavour of life to bring positive influence in the lives of people around believers.
Where there is light, darkness disappears. The verses above say Christians are to do good works so when others see their good works, they will glorify God. The verses above do not say “if you do good works” but says “when you do good works”.
Here also Christians are called to “do good” to those who hate them. Again this is a command to do good works.
This verse very clearly tells us that he who does the will of God will enter the Kingdom of Heaven.
Here Lord Jesus gave command to His disciples to preach, heal, cleanse, etc. and to do it freely. This is also the will of God for all Christians.
Here is a warning to Christians to continue doing the will of God even when iniquity abounds and love grows cold. Looking at the verses prior to these verses, we can conclude that iniquity may abound in the Church also (ref. false prophets, verse 11). Here the warning to Christians is that even if they are offended by fellow believers, if they continue doing the will of God to the end, they will be saved. Being offended by other believers does not allow followers of Christ to abandon doing the will of God and is required to be saved.